Banca de DEFESA: CARLOS ROBERTO PINHEIRO JUNIOR

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : CARLOS ROBERTO PINHEIRO JUNIOR
DATE: 28/04/2022
TIME: 08:00
LOCAL: Ambiente virtual
TITLE:

Soil Genesis and Classification in the Araripe Sedimentary Basin

KEY WORDS:

Pedogenesis. Black soils. Carbonate soils. Umbric Ferralsols.

PAGES: 121
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SPECIALTY: Gênese, Morfologia e Classificação dos Solos
SUMMARY:

Despite several lithostratigraphic and paleontological studies, little is known about the genesis of soils in the Araripe Sedimentary Basin and the main factors and processes at work, as well as the role of these soils in the storage of organic and inorganic carbon. In this study we evaluated (i) the action of pedogenesis and weathering of soils formed from shales and fine sandstones under Caatinga vegetation in Vale do Cariri; (ii) the mechanisms of organic and inorganic carbon accumulation of black soils formed from limestone under Cerrado vegetation and; (iii) characterized the main organic matter compartments of Umbric Ferralsols formed from coarse sandstones under Subcaducifolic Tropical Forest vegetation. Despite the long exposure duration of the parent material (i.e., rocks of the Jurassic age), values of Ki index (SiO₂/Al₂O₃) and Fed/Fet ratio indicate a very low degree of weathering, conditioned by a dry climate. From the MIR spectra, absorption features associated with calcite, Mg-silicate, illite, and smectite-illite interstratifications were identified. These minerals were interpreted to have originated authigenically, formed from evaporation processes in lacustrine environments. Despite the smaller influence of the relief and the low action of pedogenetic processes, incipient evidence of clay translocation is observed in the upper third of the landscape. In black soil formed from limestone, the combination of high mineral-associated organic carbon (MAOC) content, high MAOC/soil organic C ratio, and low C/N ratio indicates a high degree of transformation and stabilization the organic matter in these soils. The high 2:1 clays and exchangeable Ca²⁺ benefits the stabilization of organic C by means of organic–mineral interactions. Additionally, the dominance of carbonates of geogenic origin (limestone particles in the sand fraction) is indicative of the low dissolution of these carbonates. Through micromorphological evaluation, pedogenic carbonates were observed at the top of the B horizon of these soils, where the carbon dioxide (CO₂) pressure is lower. The variation in relief demonstrated an ostensible influence on inorganic C constrained in the lower third. This favored high humidity and root activity at depth, increasing the CO₂ pressure and hindering the re-precipitation of carbonates despite the high pH and abundance of exchangeable Ca²⁺. In the Umbric Ferralsols of the Chapada do Araripe, charcoal fragments were observed in the coarse fractions, representing an important carbon pool due to high recalcitrance. The high carbon contents of the free light fraction (C-FLF) suggest high carbon inputs by native vegetation. The high contents of residual particulate organic carbon (POCres) may have underestimated the contents of the light intraggregate fraction (C-ILF), given the low contents of C-ILF despite the fact that all horizons have a strongly developed granular structure. Due to the relevance of the light fractions, land use changes could drastically reduce the carbon content in the Umbric Ferralsols of the Chapada do Araripe.

 

BANKING MEMBERS:
Externo à Instituição - FABIO SOARES DE OLIVEIRA - UFMG
Externo à Instituição - JOLIMAR ANTONIO SCHIAVO - UEMS
Presidente - 1060711 - MARCOS GERVASIO PEREIRA
Externo à Instituição - MILTON CÉSAR COSTA CAMPOS - UFPB
Externa à Instituição - SHEILA APARECIDA CORREIA FURQUIM - UNIFESP